The present invention relates to an electrical wiring box and, more particularly, to an electrical wiring box having factory-installed mounting elements associated therewith for permitting the quick and easy mounting of an electrical device within the wiring box in a field installation.
At the present time electrical devices such as receptacles and switches are most commonly mounted within electrical wiring boxes by means of screws associated with the electrical devices and threaded into openings provided in ears or bosses of the wiring boxes. Since the screws are usually of fine pitch and of considerable length, to accommodate several possible thicknesses of wallboard or panelling, considerable time is required to completely thread a pair of the screws into the tabs or bosses of a wiring box to tightly secure an electrical device to the wiring box. As a result, and in the interest of reducing escalating labor costs, it has been found highly desirable to reduce the time and effort required to mount electrical devices within wiring boxes.
Numerous attempts have been made and several proposals offered directed to a solution to the above-stated problem. By way of example, in U.S. Pat. No. 3,403,214, there is described an electrical device (receptacle or switch) having a strap portion associated therewith and a pair of fasteners used in conjunction with openings in the strap portion for mounting the electrical device to a pair of mounting ears of an electrical wiring box. One of the fasteners is a conventional mounting screw adapted to be inserted into a first opening in the strap portion of the electrical device and to be threaded into a threaded opening of one of the ears of the wiring box, and the other fastener is a special elongated serrated member extending normally from the strap portion and adapted to be freely inserted into a threaded opening of the other ear of the wiring box. To mount the electrical device to the wiring box, the special serrated fastener is first freely inserted completely within the opening of the associated ear and the mounting screw is then threaded into the threaded opening of its associated ear. As the mounting screw is threaded into its associated ear opening, a part of the strap portion of the electrical device physically coacts with the mounting screw and causes the electrical device to move along a longitudinal axis thereof to cause the serrations of the serrated fastener to move into physical contact with and firmly engage the threads of its associated ear opening. As a result, the electrical device is attached to the wiring box. Variations and modifications of the above-described arrangement, utilizing electrical devices having specially-modified strap portions and special serrated or threaded fasteners, are also described in U.S. Pat. Nos. 3,403,215 and 3,403,216. Further, in U.S. Pat. No. 3,403,218, there is described a mounting arrangement utilizing an electrical device having a specially-modified strap portion and a pair of special eccentric mounting screws, the latter screws being freely and fully insertable within threaded openings in associated ears and then capable of rotation to cause the threads thereof to move into physical contact with and engage the threads of the associated threaded ear openings.
Still other solutions to the aforedescribed problem are described in U.S. Pat. Nos. 3,526,703, 3,876,821 and 3,895,732. In U.S. Pat. No. 3,526,703, a mounting arrangement is described which includes a pair of side-by-side mounting lugs mounted for pivotal movement on each of two opposing walls of a wiring box. The mounting lugs of each pair of lugs have adjacent threaded concavities cooperating to define an internally-threaded opening for threadably receiving therein an associated screw for mounting an electrical device to the wiring box. To mount the electrical device to the wiring box, a pair of screws are first pushed for essentially their full length through the openings defined in the pairs of lugs. This pushing action causes the lugs of each pair to move away from each other. The screws are then tightened for a few turns as a result of which the lugs of each pair move back toward each other to provide securement of the electrical device to the wiring box.
In U.S. Pat. No. 3,876,821, a mounting arrangement is described which includes a pair of insert members, each fixedly disposed within a corresponding opening or channel in a boss of a wiring box and each having a thread-engaging tab portion adapted to physically engage a region between adjacent threads of a screw following the insertion of the screw into the opening. To mount an electrical device to the wiring box, the screws associated with the electrical device are pushed into the openings in the bosses of the wiring box, causing the thread-engaging tab portions of the insert members to deflect outwardly slightly as the screws pass into the openings. When the screws have been pushed completely into the openings, the thread-engaging tab portions fall between and come to rest between adjacent threads of the screws, thereby mounting the electrical device within the wiring box.
In U.S. Pat. No. 3,895,732, a mounting arrangement is described which includes a pair of generally triangular-shaped screw-retaining clips which are arranged to be inserted into corresponding generally triangular-shaped openings in a wiring box. Each of the clips has a plurality of tines for physically cutting or biting into the walls of the corresponding opening of the wiring box, thereby to secure the clip to the wiring box, and each of the clips has a plurality of thread-engaging flanges or tips disposed within the associated opening for engaging a screw inserted into a central region of the clip. To mount an electrical device within the wiring box, the screws associated with the electrical device are pushed into the central regions of the screw retaining clips, causing the thread-engaging flanges to deflect outwardly slightly as the screws pass into the central regions. When the screws have been inserted completely into the central regions of the clips, the thread-engaging flanges fall between and come to rest in different regions between threads of the screws thereby gripping onto the screws.
While the mounting arrangements of the aforedescribed patents appear to represent reasonable solutions to the problem of mounting electrical devices within wiring boxes, these mounting arrangements have a number of disadvantages associated therewith. Specifically, in the case of U.S. Pat. Nos. 3,403,214; 3,403,215; 3,403,216 and 3,403,218, the mounting arrangements described therein require specially-modified electrical devices (strap portions) and special fasteners (serrated mounting members and mounting screws), all of which are difficult and costly to manufacture. In the case of U.S. Pat. No. 3,526,703, the mounting arrangement described therein, utilizing two pairs of pivoting lugs mounted to a wiring box and each having a threaded concavity therein, is also difficult and costly to manufacture, particularly on a mass-production, volume basis, and especially if the wiring box with which the mounting arrangement is to be used is of a molded plastic composition. In the case of U.S. Pat. No. 3,876,821, the insert members may be rendered inoperative if particles of plasterboard, drywall or other material get into an insert member and/or the threads of a mounting screw and prevent the thread-engaging tab portion of the insert member from engaging the region between adjacent threads of the mounting screw. In this situation, the thread-engaging tab portion of the insert member, rather than engaging a region between adjacent threads of the screw, may instead ride on the rim of a thread of the screw, leading to the possible undesirable removal of the screw from the insert member and, thus, the possible loosening or, even worse, the withdrawal of the electrical device from the wiring box. The insert members of U.S. Pat. No. 3,876,821 further require means other than the thread-engaging tab portions themselves, for example, locking tabs cooperating with shoulders or abutments within the openings, for retaining the insert members in position, thereby further complicating the design of the insert members and the wiring box itself. In the case of U.S. Pat. No. 3,895,732, the retention of the screw-retaining clips in the openings in the wiring box is accomplished entirely by the physical cutting or biting effects of the small tines of the clips. While this type of biting action may be suitable for "soft" (e.g., thermoplastic) plastic boxes, it cannot, by itself, practicably be achieved with "hard", brittle (e.g., thermosetting) plastic boxes. Further, the movement of the thread-engaging flanges in a direction generally transverse to the axes of the openings is very limited, by virtue of the fact that the portions of the clips supporting the thread-engaging flanges are physically confined within the openings, requiring substantial force to be applied to the screws to spread the thread-engaging flanges apart sufficiently to easily and readily receive the screws.